line on a poly kayak or canoe. The sandwich layered nature of Royalex places limits on how sharply it can be molded and keep adequate strength. But some poly canoes, including the OT Discovery series, have a sandwich construction also, with foam in between hard poly layers.
If a poly sandwich Discovery with a sharp bow runs into something sharp and hard, at full speed and with a full load, the bow may be bent badly enough that heat won't coax it back into shape.
As for Royalex, the blunt bows of some whitewater canoes are very hard to damage. But Wenonah and some other makers mold Royalex boats with fairly sharp bows, and those bows are more susceptible to permanent damage if the boat pitons a rock.
Royalex is better for medium to large canoes, in terms of lower weight, somewhat better stiffness, and repairability. Poly construction starts to work really well for small solo canoes such as the Esquif L'edge. Their small size and rocker contributes to stiffness, and like poly kayaks, they are very resistant to damage.
Cartop Kayak Carriers
Recreational Kayak Paddle